Erbium-Activated Silica-Hafnia: a Reliable Photonic System

Sol gel-derived silica-hafnia is a reliable and flexible binary system that has proved to be suitable for rare earth doping and fabrication of amorphous and glass ceramic planar waveguides as well as for improving thermal stability of spherical microresonators. Here we present an overview concerning fabrication protocols and structural, optical and spectroscopic assessment of SiO
₂
-HfO
₂
waveguides activated with Er
³⁺
ions. In order to put in evidence the reliability and versatility of the silica-hafnia system for photonics applications three different confined structures are briefly presented: i) amorphous waveguides; ii) glass-ceramic waveguides; iii) coated microspheres.